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Mutant Gonorrhea: A Statistical Analysis

Mutant Gonorrhea: A Statistical Analysis. Lauren Myers Theory of Statistics. The Organism. Neisseria gonorrhoeae Etiological agent of gonorrhea Type IV Pili ( Tfp ) are an important virulence factor Filamentous appendages Through cycles of adhesion, retraction, and release, they mediate:

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Mutant Gonorrhea: A Statistical Analysis

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  1. Mutant Gonorrhea:A Statistical Analysis Lauren Myers Theory of Statistics

  2. The Organism • Neisseriagonorrhoeae • Etiological agent of gonorrhea • Type IV Pili (Tfp) are an important virulence factor • Filamentous appendages • Through cycles of adhesion, retraction, and release, they mediate: • Twitching motility • DNA uptake • Host cell adhesion • Host cell invasion • The pilus is assembled from many constituent proteins • PilC, PilE, PilT, Gcp, etc…

  3. The Experiment • Generated null Gcp mutant • Mutant retracted Tfp with much greater force • Mutant had increased invasion index • Generated inducible Gcp mutant (IF_1β_4) • Uninduced strain should have mutant phenotype • Induced strain should have wild type phenotype • Unable to demonstrate consistent invasion phenotype • Fe2+ regulation of Gcp • Are we inducing Gcp correctly? • Statistical analysis may justify time and expense to investigate this question

  4. The Data • X and Y are normally distributed random variables, representing the invasion indices of the induced and uninduced mutant, respectively • Table I: Invasion Indices of Induced & Uninduced IF_1β_4 • nX = nY = 10 • X = 0.0693% • Y = 0.0831%

  5. The Statistical Analysis • X and Y have unknown population means μX and μY, respectively • H0: μX = μY against H1: μX ≠ μY • T-statistic: • Critical region: equal tails of Student t-distribution • |t| > t0 • Degrees of freedom = μX + μY -2

  6. The Statistical Analysis • Evaluate t-statistic to obtain: t = -0.3004 • Obtain t0 from table: • Degrees of freedom = 18 • According to convention, α = 0.05 • t0 = 2.1009 • Clearly, |t| < t0 • Accept the null hypothesis: H0: μX = μY • There is no significant difference between the invasion indices of the induced and uninduced mutant

  7. Conclusions and Future Directions • Confirmed that my experiments did not show a difference in invasion phenotype • New experiments showed Gcp levels do change over the course of infection • We have conducted our first experiments under fundamentally unnatural conditions • Future experiments: time induction to coincide with natural increase in Gcp expression • Repeat invasion assays; compare population means using the same analysis

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